Methods and devices to prevent fluid migration in a refrigeration system during an off cycle

ABSTRACT

Embodiments to prevent Off Cycle fluid migration in a refrigeration system are described. The embodiments described herein allow a fluid, such as oil from a crankcase sump of a compressor of the refrigeration system, to flow into an anti-fluid migration apparatus positioned in-line along a suction line of the refrigeration system. The fluid can be accumulated in the anti-fluid migration apparatus. The accumulated fluid may form a fluid flow barrier to prevent Off cycle refrigerant migration in the suction line.

FIELD OF TECHNOLOGY

The embodiments disclosed herein relate generally to a refrigeration system. More particularly, the embodiments relate to preventing refrigerant migration to a compressor in, for example, a transport refrigeration system during an Off cycle of the refrigeration system.

BACKGROUND

A transport refrigeration system may use a vapor-compression type refrigeration system to control the temperature of an internal space of a transport unit, such as a temperature controlled trailer unit or a truck. The vapor-compression type refrigeration system is generally a closed circuit. A refrigerant can be compressed by the compressor and circulated in the closed circuit to transfer heat from the internal space of the transport unit to the outside environment. During operation, a user may set a target temperature point, i.e. a setpoint, for the internal space. In an On cycle of the refrigeration system, the compressor of the refrigeration system can keep operating until the target temperature point is reached. At that point, the refrigeration system may enter into an Off cycle, in which the compressor of the refrigeration system stops. When the temperature of the internal space exceeds a permitted deviation range from the target temperature point, the compressor can start up from the Off cycle and resume running. The refrigeration system can repeat the On and Off cycles to maintain the temperature of the internal space within the permitted deviation range. The refrigeration system can also be configured to be in the off cycle in other situations. For example, the refrigeration system can be in the Off cycle overnight and back to the On-cycle during the daytime.

SUMMARY

Embodiments to prevent Off Cycle fluid migration to a compressor of a refrigeration system are described. The embodiments described herein may allow fluid, such as oil, from a crankcase sump of the compressor to flow into an anti-fluid migration apparatus positioned in-line within a suction line of the refrigeration system, and accumulate in the anti-fluid migration apparatus. The accumulated oil in the anti-fluid migration apparatus may form a fluid barrier or seal to prevent Off cycle fluid (such as refrigerant) migration from other components of the refrigeration system to the compressor through the suction line.

In one embodiment, a method to prevent Off cycle refrigerant migration may include turning off the compressor of the refrigeration system; directing a lubricant from the compressor to accumulate in an anti-fluid migration apparatus positioned in-line along a suction line of the refrigeration system so that the lubricant accumulated in the anti-fluid migration apparatus forms a fluid barrier or seal to prevent fluid from flowing to the compressor through the suction line; turning on the compressor; and directing the lubricant accumulated in the anti-fluid migration apparatus to flow from the anti-fluid migration apparatus to the compressor through the suction line.

In some embodiments, the method may include preventing a fluid flow through a conduit connected between the anti-fluid migration apparatus and the crankcase sump during an Off cycle.

In another embodiment, a refrigeration system with an anti-fluid migration apparatus to prevent Off cycle fluid migration is also provided. In some embodiments, the refrigeration system may have a crankcase sump that is configured to contain oil with an oil level plane when the refrigeration system is in an Off cycle. The crankcase sump may have an opening that is positioned below a minimal oil level plane and a suction line connected to the crankcase sump. In some embodiments, the refrigeration system may include an anti-fluid migration apparatus that has a trap positioned in-line along the suction line and a conduit. The trap may have a flow passage, at least a section of which is positioned below the minimal oil level plane in the crankcase sump. The conduit may have a first end and a second end. The first end may be in fluid communication with the flow passage and the second end may be in fluid communication with the opening of the crankcase sump.

In some embodiments, the refrigeration system may have a flow control device positioned in-line along the conduit between the first end and the second end. In some embodiments, the flow control device may have an “open” state that generally allows oil (or any other types of fluid) in the crankcase sump to flow to the trap through the conduit, and an “off” state that generally prevents an oil flow between the crankcase sump to the trap through the flow control device. In some embodiments, the flow control device may be in the “open” state when the refrigeration is in an Off cycle, and in the “closed” state when the refrigeration system is in an On cycle. In some embodiments, the flow control device may be an orifice in the conduit.

In some embodiments, the trap of the anti-fluid migration apparatus may be a U-shaped section of the suction line.

In yet another embodiment, a transport refrigeration system with an anti-fluid migration apparatus is provided. The anti-fluid migration apparatus may include a trap that has a flow passage positioned in-line along a suction line of the refrigeration system. The anti-fluid migration apparatus may also include a conduit having a first end and a second end. The first end of the conduit may be in fluid communication with the flow passage of the trap. The second end of the conduit may be in fluid communication with a crankcase sump of the compressor. The trap may be configured to receive fluid flowing through the conduit, and allow the fluid to accumulate in the trap in order to form a fluid barrier or seal to prevent fluid migration from components of the refrigeration system to the compressor through the flow passage.

In some embodiments, the conduit may be equipped with a flow control device that is positioned in-line between the two ends of the conduit. The flow control device may have an “open” state that generally allows oil in a crankcase sump of the refrigeration system to flow to the trap through the conduit, and an “off” state that generally prevents oil flow between the crankcase sump to the trap through the conduit. In some embodiments, the flow control device is in the “open” state when the refrigeration is in an Off cycle, and in the “closed” state when the refrigeration system is in an On cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers represent corresponding parts throughout.

FIG. 1 illustrates a side schematic view of a transport temperature controlled trailer unit with a transport refrigeration system.

FIG. 2 illustrates a flow chart of an embodiment of a method to prevent Off cycle refrigerant migration.

FIG. 3A illustrates a side schematic view of a portion of a refrigeration system with an embodiment of an anti-fluid migration apparatus when the refrigeration system is in an On cycle.

FIG. 3B illustrates a side schematic view of the portion of a refrigeration system as shown in FIG. 3A during an Off cycle.

FIG. 4 illustrates a side schematic view of a portion of a refrigeration system with another embodiment of the anti-fluid migration apparatus.

DETAILED DESCRIPTION

The embodiments described herein relate to preventing refrigerant migration to a compressor in a transport refrigeration system during an Off cycle of the refrigeration system.

In a refrigeration system, a lubricant, such as mineral or synthetic oil, is generally used to lubricate moving parts of the compressor. During an Off cycle of a refrigeration system, particularly during a long Off cycle (e.g. over 4 hours), a fluid such as a refrigerant in a vapor state may be driven into a crankcase sump of a compressor from other components of the refrigeration system, such as an accumulator. This fluid is driven into the crankcase sump at least due to the vapor pressure of the refrigerant being greater than that of a lubricant. In these embodiments, the refrigerant is in a liquid form when the refrigerant is in the crankcase sump.

The refrigerant migrated into the crankcase sump may dilute the lubricant in the crankcase sump and consequentially reduce the effectiveness of the lubricant. In some cases, it has been observed that the liquid refrigerant can completely fill the crankcase of the compressor during an Off cycle of the compressor. If the compressor starts up with an excessive amount of liquid refrigerant in the crankcase sump, the load on bearings and/or an Oldham coupling, as well as any moving parts of the compressor may increase. In some cases, the lubricant in the crankcase sump and the liquid refrigerant migrated into the crankcase sump may form two separated liquid layers during an Off cycle. In some cases, oil floats on the liquid refrigerant because the oil density may be less than the density of the refrigerant, and during startup the oil will be pumped out of the compressor. If the compressor starts up under such a condition, the lubricant inside the crankcase sump may drop below the minimal level required for the compressor to work properly after start up. This may cause bearings/Oldham coupling fractures and wear on the moving parts of the compressor.

In the following description of the illustrated embodiments, a method to prevent fluid migration, particularly prevent Off cycle refrigerant migration to a compressor from other components of a refrigeration system is described. In an Off cycle of the refrigeration system, the method described herein can direct a lubricant in the crankcase sump of the compressor to an anti-fluid migration apparatus to form a fluid barrier or seal in the suction line to prevent refrigerant migration. Further, during start up, the method described herein can direct the lubricant accumulated in the anti-fluid migration apparatus during the Off cycle to the compressor to provide lubrication to the compressor.

Moreover, an anti-fluid migration apparatus and a refrigeration system with an anti-fluid migration apparatus to prevent fluid migration, particularly prevent Off cycle refrigerant migration to a compressor from other components of a refrigeration system are described. The anti-fluid migration apparatus may generally have a trap and a conduit that allows oil (or other types of fluid) in the crankcase sump to flow from the crankcase sump to the trap during an Off cycle. The trap may be positioned in-line along a suction line of the refrigeration system, so that the oil flowing to the trap may form a fluid barrier or seal in the trap to prevent Off cycle refrigerant migration through the suction line. The oil in the trap may be directed to the compressor during start up to provide lubrication to the compressor.

References are made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration of the embodiments in which the anti-fluid migration apparatus may be practiced. The term “Off cycle” generally means that the compressor of the refrigeration system is off, or is not pumping/circulating the refrigerant. The term “On cycle” or “in operation” generally means that the moving parts of the compressor are in motion, or is pumping/circulating the refrigerant. The term “in-line” generally means “in fluid communication” or connected. In particular, if a device is positioned in-line along a pipe, it means that a fluid flowing from first end to the second end of the pipe will generally flow through the device. If not specified, a flow control device or a valve generally has an “open” state that generally allows fluid flow through the flow control device or the valve, and a “closed” state that generally blocks the fluid flow through the flow control device or the valve. It is to be understood that the terms referring to the different types of fluids in the refrigeration system, for example, “liquid refrigerant,” “vapor refrigerant,” “oil” and “lubricant” are exemplary and not meant to be exclusive. The refrigeration system may contain any other suitable types of fluid. In addition, it is to be understood that the terms are only referred to the main components of the fluid. For example, oil may contain some refrigerant contents, and the liquid refrigerant may contain some oil. It is also to be understood that the terms used herein are for the purpose of describing the figures and embodiments and should not be regarding as limiting the scope of the present application.

Embodiments as described herein can be generally used in a temperature controlled semi-trailer truck 100 as illustrated in FIG. 1. The semi-trailer truck 100 has a tractor unit 110 that is configured to tow a temperature controlled trailer unit 120. The trailer unit 120 is installed on a frame 130. A transport refrigeration system 140 is installed on a side wall of the trailer unit 120. The transport refrigeration system 140 is configured to transfer heat between an internal space 125 and the outside environment. The refrigeration system 140 has a compressor 145. The compressor 145 generally contains a lubricant such as oil 150 inside a crankcase sump 155 to lubricate the moving parts of the compressor 145. (See below for more discussions regarding embodiments of the refrigeration system.)

It will be appreciated that the embodiments described herein are not limited to trucks and trailer units. The embodiments described herein may be used in any other suitable temperature controlled apparatuses. The refrigeration system may be a vapor-compressor type refrigeration system, or any other suitable refrigeration systems that use refrigerant. The embodiments described herein can also be generally used in any type of lubricated mechanical compressor.

Referring to FIG. 2, an embodiment of a method 200 to prevent Off cycle refrigerant migration is described. As show in FIG. 2, at 201 the compressor of the refrigeration system is operating in an On cycle, and the compressor drives a refrigerant through the refrigeration system to transfer heat from a space, for example the internal space 125 of the trailer unit 120 as shown in FIG. 1, to the environment. At 202, a temperature control circuit is configured to measure the temperature in the space, and if the temperature in the space reaches a pre-set target temperature, the control unit turns the compressor off. At 203, the refrigeration system enters into an Off cycle when the compressor of the refrigeration system is turned off.

It should be noted that the compressor of the refrigeration system may also be turned off by other methods or in other situations. In some embodiments, the compressor may be turned off by manually cutting off power supply to the compressor. In some embodiments, the compressor may be turned off, for example at night, then be turned on during the daytime.

During the Off cycle, at 204, a lubricant in the crankcase sump of a compressor is generally directed to an anti-fluid migration apparatus that is positioned in-line along a suction line of the refrigeration system.

The anti-fluid migration apparatus may be positioned between an accumulator and an inlet of the compressor. In some embodiments, the anti-fluid migration apparatus may have a side conduit that is connected to the crankcase sump of the compressor. The conduit may have a valve. During an Off cycle, the valve may be in an “open” state that allows the lubricant in the crankcase sump to flow to the anti-fluid migration apparatus through the conduit. The lubricant flowing to the anti-fluid migration apparatus can accumulate in the anti-fluid migration apparatus and/or the suction line, and is able to form a fluid barrier or seal in the anti-fluid migration apparatus that prevent refrigerant migration in the suction line from, for example, the accumulator to the inlet of the compressor. (Not shown.)

At 205, the refrigeration system remains in the Off cycle and waits for the On cycle. The compressor can be turned on for example by using the temperature control circuit. As shown in FIG. 2, at 206, the temperature control circuit is configured to determine whether the temperature in the space exceeds for example a deviation range from the target temperature. If the range is exceeded, the method proceeds to 207. At 207, the control circuit starts up the compressor from the Off cycle, and the compressor enters an On cycle and resumes working to compress the refrigerant, which is shown in FIG. 2 as 207. If the range is not exceeded, the method proceeds to 205, and the refrigeration system remains in the Off cycle.

At 207, when the compressor starts up, the lubricant accumulated in the suction line and/or the anti-fluid migration apparatus is directed into the inlet of the compressor via the suction line. The lubricant getting into the compressor may lubricate the compressor.

During the On cycle, at 208, the lubricant is generally prevented from flowing between the crankcase sump and the anti-fluid migration apparatus through the conduit connecting the crankcase sump and the anti-fluid migration apparatus. This can be accomplished by setting the valve on the conduit to a “closed” position. (Not shown.) It should be noted that 208 may be performed in the Off cycle too. For example, 208 may be performed right after the anti-fluid migration apparatus is filled with the lubricant from the crankcase sump at 204.

FIG. 3A provides an embodiment of a refrigeration system 300 with an anti-fluid migration apparatus to prevent fluid migration during an Off cycle. In the embodiment, a compressor 308 has an outlet 309 that is configured to allow a refrigerant to flow out of the compressor 308, and an inlet 350. The anti-fluid migration apparatus includes a trap 320 and a conduit 322. The trap 320 is configured to have a flow passage 326 that is positioned in-line along a suction line 301 between an accumulator 305 and the inlet 350 of the compressor 308. The suction line 301 is connected to the compressor 308 at an inlet 350 of the compressor 308.

The conduit 322 has two ends. A first end of the conduit 322 is connected to a side opening 340 of the trap 320 as shown in FIG. 3A, and forms a fluid communication with the flow passage 326. A second end of the conduit 320 is connected to an opening 317 of the crankcase sump 330 of the compressor 308, and form a fluid communication with the crankcase sump 330. The crankcase sump 330 is configured to contain oil 303 that can be used to lubricate the compressor 308. The conduit 322 is generally equipped with a flow control device 321 to control a fluid flow between the crankcase sump 330 and the trap 320.

To facilitate the connection of the conduit 322 to the crankcase sump 330 of the compressor 308, a valve 307 may be equipped to the crankcase sump opening 317 as shown in FIG. 3A. The valve 307 may be configured to be in a “closed” state until the conduit 322 is installed between the trap 320 and the crankcase sump 330. The valve 307 may be in an “open” state after the conduit 322 is connected to the crankcase sump 330, and may be closed when necessary. Preferably, the valve 307 may be a Schrader type valve so that the conduit 322 may be attached to the valve 307 easily during the installation of the refrigeration system 300. The Schrader type valve may generally have a center pin that is connected to a seal of the valve, and a spring pushing against the seal to close the valve in a normal condition. Therefore, if the center pin is not pushed, the Schrader valve may be generally sealed. If the center pin is pushed, the seal of Schrader valve may be pushed away against the spring bias causing the valve to open. In some embodiments, when the valve 307 is a Schrader valve, the valve 307 may generally remain sealed without attaching the conduit 322 to the valve. After the center pin is pushed by connecting the conduit 322 to the Schrader type valve 307, the Schrader type valve 307 may be opened. The Schrader type valve 307 may also eliminate the need to remove oil from the compressor before installing a line between the crank case 330 and the trap 320, if the compressor contains oil.

When the refrigeration system 300 is in operation, a bottom 315 of the compressor 308 is typically installed on a flat surface that is generally parallel to the frame on which the refrigeration system 300 rests, such as the trailer frame 130 as shown in FIG. 1. The crankcase sump 330 generally contains oil 303 when the refrigeration system 300 is in operation. The oil 303 may have an oil level L1(on) as shown in FIG. 3A when the compressor 308 is in operation, i.e. when the refrigeration system is in an On cycle. It should be noted that L1(on) may be different when the refrigeration system 300 is in different On cycles, i.e. L1(on) may vary from one On cycle to another On cycle. It should also be noted that the oil level L1(on) can vary during the operation of the refrigeration system in one On cycle.

The top surface of the oil level, L1(on) or L1(off) (as discussed below) in the crankcase sump 330 defines an oil level plane 310 that is generally parallel to the trailer frame on which the refrigeration system 300 rests. The opening 317 of the crankcase sump 330 is generally positioned below the oil level plane 310 of L1(on). In some embodiments, the opening 317 may be positioned below a minimal oil level in the crankcase sump 330 when the refrigeration system 300 is in operation. The minimal oil level may be the minimal amount of oil required for the compressor 308 to perform properly. As shown in FIG. 3A, the opening 317 is on the side wall of the crankcase sump 330 and is positioned immediately above the bottom 315. In some other embodiments, the opening 317 may be in the bottom 315, rather than in the side wall(s) of the crankcase sump 330.

Referring now to FIG. 3B, the refrigeration system 300 with a trap 320 during an Off cycle is shown. The crankcase sump 330 has oil 303 at an oil level L1(off) during an Off cycle. It should be noted that L1(off) may be different from L1(on). In some cases, L1(on) may be lower than L1(off). It should also be noted that L1(off) may be different when the refrigeration system 300 is in different Off cycles, i.e. L1(off) may vary from one Off cycle to another Off cycle.

The trap 320 is a U-shaped section of the suction line 301 between the accumulator 305 and the inlet 350 of the compressor 308 as shown in both FIGS. 3A and 3B, and the flow passage 326 is a section of the suction line 301. It should be noted that the trap 320 may have different shapes and configurations. Generally, the flow passage 326 is positioned in-line along the suction line 301. The flow passage 326 may have a diameter that is the same as the diameter of the suction line 301, or the diameter of the flow passage 326 may be different from the diameter of the suction line 301. The trap 320 may be generally configured to receive oil 303 flowing from the crankcase sump 330 and allows the oil 303 to accumulate in the trap 320 during an Off Cycle.

As shown in FIG. 3B, after the refrigeration system 300 is assembled for example in a transport unit such as the transport refrigeration unit 100 as shown in FIG. 1, at least a section of the flow passage 326 is positioned below the oil plane 310 of L1(off). The side opening 340 of the trap 320 and the crankcase sump opening 317 are also generally positioned below the oil plane 310 of L1(off).

The flow control device 321 may generally have an “open” state that allows a fluid flow through the flow control device 321, and a “closed” state that generally blocks the fluid flow through the flow control device 321. In the embodiment as shown in FIGS. 3A and 3B, the flow control device 321 is a check valve positioned in-line along the conduit 322 between the side opening 340 of the trap 320 and the crankcase sump opening 317. Preferably, the flow control device 321 may be a normally-open solenoid check valve that is configured to have a “closed” state that prevents a fluid flow between the crankcase sump 330 and the trap 320 through the conduit 322, as shown in FIG. 3A, and an “open” state that allows a fluid flow between the trap 320 and the crankcase sump 330 through the conduit 322 as shown in FIG. 3B.

In operation, when the refrigeration system 300 is in an On cycle as shown in FIG. 3A , a refrigerant can flow in the suction line 301 in a direction as shown by arrows from the accumulator 305 to the inlet 350 of the compressor 308. The flow passage 326 is configured to allow a refrigerant to pass through. The compressed refrigerant may exit the compressor 308 through the compressor outlet 309 and flow to other components of the refrigeration system 300. The flow control device 321 may remain in the closed state to prevent an oil flow between the crankcase sump 330 and the trap 320 through the conduit 322.

When the refrigeration system 300 enters an Off cycle (as shown in FIG. 3B) from the On cycle (as shown in FIG. 3A), the flow control device 321 is switched to the “open” state to allow a fluid flow between the crankcase sump 330 and the trap 320 through the conduit 322. Since the crankcase sump opening 317, the side opening 340 and the flow passage 326 of the trap 320 are all positioned below the oil level plane 310 of L1(off), oil 303 in the crankcase sump 330 can be driven into the trap 320 through the conduit 322 by gravity and may accumulate in the flow passage 326. As shown in FIG. 4, when the amount of the oil 303 accumulated in the flow passage 326 reaches a level that is sufficient to fill at least a section of the flow passage 326, the oil 303 in the trap 320 can act as a fluid barrier or a seal within the flow passage 326 that blocks fluid migration through the suction line 301, and therefore prevents refrigerant migration from for example the accumulator 305 (or other components of the refrigeration system 300) to the compressor 308 through the suction line 301 during the Off cycle.

When the refrigeration system starts up from the Off Cycle as shown in FIG. 3B, the flow control device 321 is switched to the “closed” state to prevent a fluid flow between the crankcase sump 330 and the trap 320 through the conduit 322. The oil 303 accumulated in the trap 320 during the Off Cycle returns to the crankcase sump 330 through the suction line 301 and the inlet 350 of the compressor 8 after the compressor 308 starts up. The returning oil can splash on the moving parts, bearings and/or Oldham to lubricate the compressor 308 during start up.

Generally, as shown in FIGS. 3A and 3B during the installation of the refrigeration system 300, the trap 320 may be positioned biased to the compressor 308 in the suction line 301 between the accumulator 305 and the compressor 308. In some embodiments, the trap 320 may be positioned next to the compressor 308, so that it does not require a long conduit 322 to connect the trap 320 and the compressor 308.

The trap 320 may generally be positioned so that a top of the conduit 322 is just below the minimal oil level in the crankcase sump 330. The position of the trap 320 may also be configured to avoid excessive oil accumulation inside the trap 320.

As shown in FIG. 4, in some embodiments, a flow control device 421 may be an orifice 423 positioned in-line along a conduit 422 between a trap opening 440 and a crankcase opening 417. The orifice 423 may be a portion of the flow passage of the conduit 422 that has a reduced diameter. In this configuration, a check valve (such as the check valve 321 in FIGS. 3A and 3B) may not be necessary.

If the orifice 423 is used, in some embodiments a small amount of oil may migrate from a crankcase sump 430 to a trap 420 when a compressor 408 is in operation, however the migrated oil may be sucked back into the compressor 408 through a suction line 401 and inlet 450. In some embodiments, the pressure difference between the pressure in the trap 420 and the pressure in the crankcase sump 430 may prevent an oil flow between the crankcase sump 430 and the trap 420 when the compressor 408 is in operation. During an Off Cycle, the oil 403 may flow to the trap 420 through the orifice 423 and accumulate in the trap 420 to act as a fluid barrier or seal until the compressor 408 resumes operation.

It is to be understood that components other than a crankcase sump of a refrigeration system can also provide a fluid that can accumulate in the trap and therefore prevent off cycle liquid migration. For example, in some embodiments, the refrigeration system may have an oil separator that includes an oil reservoir and is generally positioned downstream of a compressor in a suction line. The oil separator can be used to provide the oil to the trap and prevent off cycle liquid migration. It is also to be understood that some refrigeration systems may have multiple compressors. In a stationary multiple-compressor refrigeration system with a common manifold, the trap can be positioned upstream of the common manifold to prevent off cycle oil migration to one or more of the compressors.

It is appreciated the trap as described herein may be applicable to a refrigeration system with a suitable compressor, such as a reciprocating compressor, a scroll compressor and/or a screw compressor.

Aspect Section

Any aspects 1-11 can be combined with any aspects 12-20. Any aspects 12-16 can be combined with any aspects 17-20.

-   Aspect 1. A refrigeration system comprising:

a container of the refrigeration system configured to contain a fluid with a fluid level plane when the refrigeration system is in an Off cycle of the refrigeration system;

a refrigerant line;

a trap positioned in-line along the refrigerant line, the trap including a flow passage, at least a section of which is positioned lower than the fluid level plane in the container; and

a conduit in fluid communication with the flow passage and the container;

wherein the conduit is configured to allow fluid communication between the container and the flow passage of the trap when the refrigeration system is in an off cycle.

-   Aspect 2. The refrigeration system of aspect 1, further comprising:

a flow control device positioned along the conduit.

-   Aspect 3. The refrigeration system of aspects 1-2,

wherein the flow control device has an “open” state that allows fluid communication between the container and the flow passage of the trap through the conduit, and an “off” state that prevents fluid communication between the container and flow passage of the trap through the flow control device.

-   Aspect 4. The refrigeration system of aspect 3, wherein the flow     control device is in the “open” state when the refrigeration is in     an Off cycle, and in the “closed” state when the refrigeration     system is in an On cycle. -   Aspect 5. The refrigeration system of aspects 1-4, further     comprising:

a Schrader valve positioned between the container and the conduit, wherein the conduit is connected to the Schrader valve.

-   Aspect 6. The refrigeration system of aspects 2-5, wherein the flow     control device is a solenoid check valve. -   Aspect 7. The refrigeration system of aspects 2-5, wherein the flow     control device is an orifice in the conduit. -   Aspect 8. The refrigeration system of aspects 1-7, wherein the trap     is a U shaped section of the refrigerant line. -   Aspect 9. The refrigeration system of aspects 1-8, wherein the     container is a crankcase of a compressor of the refrigeration     system. -   Aspect 10. The refrigeration system of aspects 1-9, wherein the     container is an oil separator. -   Aspect 11. The refrigeration system of aspects 1-10, wherein the     refrigerant line is a suction line of the refrigeration system. -   Aspect 12. An anti-fluid migration apparatus to prevent Off cycle     fluid migration in a refrigeration system comprising:

a refrigerant line;

a trap having a flow passage, the flow passage configured to be positioned in-line of the refrigerant line; and

a conduit in fluid communication with the flow passage of the trap and a crankcase of a compressor of the refrigeration system;

wherein the flow passage of the trap is configured to receive a fluid through the conduit, and allow the received fluid to accumulate in the trap so as to form a fluid barrier to prevent fluid migration through the flow passage of the trap.

-   Aspect 13. The anti-fluid migration apparatus of aspect 12, wherein     the flow control device has an “open” state that generally allows     fluid communication between the crankcase sump and the flow passage     of the trap through the conduit, and an “off” state that generally     prevents fluid communication between the crankcase sump and the trap     through the conduit. -   Aspect 14. The anti-fluid migration apparatus of aspects 12-13,     wherein the flow control device is in the “open” state when the     refrigeration is in an Off cycle, and in the “closed” state when the     refrigeration system is in an On cycle. -   Aspect 15. The anti-fluid migration apparatus of aspects 12-14,     wherein the flow control device is an orifice in the conduit. -   Aspect 16. The anti-fluid migration apparatus of aspects 12-15,     wherein the refrigerant line is a suction line of the refrigeration     system. -   Aspect 17. A method of preventing Off cycle fluid migration in a     refrigeration system comprising:

during an Off cycle of the refrigeration system, directing a first fluid from a container of the refrigeration system to accumulate in a section of a refrigerant line of the refrigeration system; and

forming a fluid barrier in the section of the suction line with the first fluid accumulated in the section of the suction line to prevent a second fluid from flowing in the suction line.

-   Aspect 18. The method of aspect 17 further comprising:

during an On cycle of the refrigeration system, directing the first fluid accumulated in the section of the suction line to flow from the section of the suction line to the container through the suction line.

-   Aspect 19. The method of aspects 17-18, wherein the first fluid is a     lubricant and the second fluid is a refrigerant. -   Aspect 20. The method of aspects 17-19, wherein the refrigerant line     is a suction line of the refrigeration system.

With regard to the foregoing description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size and arrangement of the parts without departing from the scope of the present invention. It is intended that the specification and depicted embodiment to be considered exemplary only, with a true scope and spirit of the invention being indicated by the broad meaning of the claims. 

What claimed is:
 1. A refrigeration system comprising: a container of the refrigeration system configured to contain a fluid with a fluid level plane when the refrigeration system is in an Off cycle of the refrigeration system; a refrigerant line; a trap positioned in-line along the refrigerant line, the trap including a flow passage, at least a section of which is positioned lower than the fluid level plane in the container; and a conduit in fluid communication with the flow passage and the container; wherein the conduit is configured to allow fluid communication between the container and the flow passage of the trap when the refrigeration system is in an off cycle.
 2. The refrigeration system of claim 1, further comprising: a flow control device positioned along the conduit.
 3. The refrigeration system of claim 1, wherein the flow control device has an “open” state that allows fluid communication between the container and the flow passage of the trap through the conduit, and an “off” state that prevents fluid communication between the container and flow passage of the trap through the flow control device.
 4. The refrigeration system of claim 3, wherein the flow control device is in the “open” state when the refrigeration is in an Off cycle, and in the “closed” state when the refrigeration system is in an On cycle.
 5. The refrigeration system of claim 2, further comprising: a Schrader valve positioned between the container and the conduit, wherein the conduit is connected to the Schrader valve.
 6. The refrigeration system of claim 2, wherein the flow control device is a solenoid check valve.
 7. The refrigeration system of claim 2, wherein the flow control device is an orifice in the conduit.
 8. The refrigeration system of claim 1, wherein the trap is a U shaped section of the refrigerant line.
 9. The refrigeration system of claim 2, wherein the container is a crankcase of a compressor of the refrigeration system.
 10. The refrigeration system of claim 1, wherein the container is an oil separator.
 11. The refrigeration system of claim 1, wherein the refrigerant line is a suction line of the refrigeration system.
 12. An anti-fluid migration apparatus to prevent Off cycle fluid migration in a refrigeration system comprising: a refrigerant line; a trap having a flow passage, the flow passage configured to be positioned in-line of the refrigerant line; and a conduit in fluid communication with the flow passage of the trap and a crankcase of a compressor of the refrigeration system; wherein the flow passage of the trap is configured to receive a fluid through the conduit, and allow the received fluid to accumulate in the trap so as to form a fluid barrier to prevent fluid migration through the flow passage of the trap.
 13. The anti-fluid migration apparatus of claim 12, wherein the flow control device has an “open” state that generally allows fluid communication between the crankcase sump and the flow passage of the trap through the conduit, and an “off” state that generally prevents fluid communication between the crankcase sump and the trap through the conduit.
 14. The anti-fluid migration apparatus of claim 12, wherein the flow control device is in the “open” state when the refrigeration is in an Off cycle, and in the “closed” state when the refrigeration system is in an On cycle.
 15. The anti-fluid migration apparatus of claim 12, wherein the flow control device is an orifice in the conduit.
 16. The anti-fluid migration apparatus of claim 12, wherein the refrigerant line is a suction line of the refrigeration system.
 17. A method of preventing Off cycle fluid migration in a refrigeration system comprising: during an Off cycle of the refrigeration system, directing a first fluid from a container of the refrigeration system to accumulate in a section of a refrigerant line of the refrigeration system; and forming a fluid barrier in the section of the suction line with the first fluid accumulated in the section of the suction line to prevent a second fluid from flowing in the suction line.
 18. The method of claim 17 further comprising: during an On cycle of the refrigeration system, directing the first fluid accumulated in the section of the suction line to flow from the section of the suction line to the container through the suction line.
 19. The method of claim 17, wherein the first fluid is a lubricant and the second fluid is a refrigerant.
 20. The method of claim 17, wherein the refrigerant line is a suction line of the refrigeration system. 